Bridge plugs are well tools that are typically lowered into a cased oil or gas well and set at a desired location inside the casing to isolate pressure between two zones in the well. Retrievable bridge plugs are used during drilling and workover operations to provide a temporary separation of zones. Permanent bridge plugs are used when it is desired to permanently close off the well above a lower zone or formation when, for example, that lower zone has become non-productive but one or more upper zones remain productive. In such cases, a through tubing bridge plug may be installed without the need for pulling the tubing or killing the well. Such through tubing bridge plugs may be lowered through the tubing string on a conveyance such as a wireline, coiled tubing or the like and then set by axially compressing the packing elements of the through tubing bridge plug to expand them into contact with the inner surface of the casing to provide a seal. Once in the sealing configuration, a significant pressure differential can be created across the through tubing bridge plug. Accordingly, conventional through tubing bridge plugs include one or more anchoring assemblies that are designed to support the through tubing bridge plug in the casing. More specifically, the anchoring assemblies are required to hold the through tubing bridge plug in the casing for a sufficient time period to allow cement to be added above the through tubing bridge plug and for the cement to cure to form a permanent plug.
It has been found, however, that the use of through tubing bridge plugs is limited to wells that require only a relatively small expansion ratio between the sealing configuration of the through tubing bridge plug and the running configuration of the through tubing bridge plug. Accordingly, a need has arisen for a through tubing bridge plug that is operable to isolate pressure between two zones in the well. A need has also arisen for such a through tubing bridge plug that is operable to anchor within the casing for a sufficient time period to allow cement to be added and for the cement to cure. Further, a need has arisen for such a through tubing bridge plug that is operable to be installed in wells that require a relatively large expansion ratio between the sealing configuration of the through tubing bridge plug and the running configuration of the through tubing bridge plug.